Never! The sooner you start, the less difficulty you will have... and you will be more likely to get a decent milk supply up.
I would contact your local La Leche League leader for help and support in getting started, an visit kellymom.com for tips. You will need a pump, and you may need supplements like Fenugreek and Blessed Thistle to get things going. Some also say eating oatmeal helps. You will start stimulating production by pumping every 2-3 hours.
Finally, you need to try to latch that baby onto your breast at every feeding! It can be frustrating at first, but the more stimulation your breasts get from nursing or pumping the better.
I would also ask the ladies on the Breastfeeding/Lactation Consultant board or on the Breastfeeding board. They are a wealth of knowledge and pretty quick to respond.
Good luck!